Various proposals have been made in the past to utilize a fluorescent material, such as zinc selenide (ZnSe), in combination with gallium arsenide or aluminum gallium arsenide solar cells to absorb the shorter wavelengths of solar flux (not able to directly excite a photovoltaic solar cell) and then re-emit the absorbed energy as longer wavelength fluorescence. This longer wavelength fluorescence may then be transmitted into the solar cell where it produces an output of electrical power additional to that produced by direct absorption of solar flux by the cell itself. Examples of such proposals are those made by H. J. Hovel et al, "The Effect of Fluorescent Wavelength Shifting on Solar Cell Spectral Response," Solar Energy Materials 2, (1979), pp. 19-29; and D. Walsh et al, "ZnSe Solar Spectrum Converter for GaAs Solar Cells," IEEE, 14th Photovoltaic Specialists Conference, (1980), pp. 476 and 477.
The problem with both of the above proposals is their failure to teach how to construct either a practical or a commerically feasable solution to the problem of physically combining and optically matching the fluorescent zinc selenide wavelength shifting material and the gallium arsenide or aluminum gallium arsenide solar cell. This construction must be done in such a manner as to protect the solar cell from ultraviolet radiation and proton damage while simultaneously enhancing its collection efficiency. The present invention provides a novel solution to the latter problem.